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Warming promotes cold-adapted phytoplankton in temperate lakes and opens a loophole for Oscillatoriales in spring

Authors

  • TOM SHATWELL,

    1. Hochschule Magdeburg-Stendal, Fachbereich Wasserwirtschaft, D-39011 Magdeburg, Germany,
    2. Leibniz-Institut für Gewässerökologie und Binnenfischerei, D-12587 Berlin, Germany,
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  • JAN KÖHLER,

    1. Leibniz-Institut für Gewässerökologie und Binnenfischerei, D-12587 Berlin, Germany,
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  • ANDREAS NICKLISCH

    1. Leibniz-Institut für Gewässerökologie und Binnenfischerei, D-12587 Berlin, Germany,
    2. Institut für Biologie, Humboldt-Universität zu Berlin, D-10099 Berlin, Germany
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Tom Shatwell, Leibniz-Institut für Gewässerökologie und Binnenfischerei, Müggelseedamm 301, D-12587 Berlin, Germany, tel. +49 30 641 81 692, fax +49 30 641 81 682, e-mail: shatwell@igb-berlin.de

Abstract

The effects of the recent warming trend in many northern temperate lakes on the species composition of spring phytoplankton remain poorly understood, especially because a recent change in nutrients has complicated efforts, and previous studies have defined spring according to the calendar. We analysed data from 1979 to 2004 from Lake Müggelsee (Berlin, Germany), using physical and biological parameters to define the spring period. We show that a change in timing of spring plankton events in warm years led to the paradox of lower mean water temperatures during the growth period, favouring cold-adapted diatoms over cyanobacteria, and within the diatoms, some cold-adapted centric forms over pennate forms. Under high P : Si ratios, the increased time between phytoplankton and cladoceran peaks opened a loophole for filamentous cyanobacteria (Oscillatoriales) in warm years to establish dominance after the diatoms, which are silicate limited. Therefore, the warming trend promotes filamentous cyanobacteria, a well-known nuisance in eutrophic lakes, and surprisingly, cold-adapted diatoms.

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